Processes of dewaxing oils



Nov. 5, 1946. E. M, DONS ET AL 2,410,483

PROCESS OF DEWAXING OILS Filed NOV. 13, 1944 O G. MAURO BY YYWMMQ va MW ATTORNEYS.

DEWAXED OIL SOLLJT \ON Patented. Nov. 5, 1946 PROCESSES F DEWAXING GILS Eddie M. Dons and Oswald G. Mauro, Tulsa, Okla.,

assignors to Mld-Continent Petroleum Corporation, Tulsa., Okla., a corporation of Delaware Application November 13, 1944, serial No. 583,284

2 Claims. (Cl. 196-18) This invention relates to processes of dewaxing oils wherein selective dewaxing solvents are em- [ployed to aid in solidliying the wax, The apparatus herein shown is claimed in a patent application filed by us on November 17, 1944, Serial No. 563,814. An object of the invention is to produce wax crystals that can be eiiiciently separated from the oil solution Without retaining the usual excessive quantities of oil solution in the separated wax. Prior to this invention, the wax has been precipitated and transmitted to a filter, or other separating apparatus, in the form of non-uniform crystals which are not efficiently separated'from the oil solution. For example, in a filtering operation, a mixture of non-uniform wax crystals will tend to reduce the rate of ltration while also trapping excessive quantities of oil solution in the wax cake on the surface of the filter.

For many years, this objectionable condition has been clearly recognized and well understood by the experts in this art, and eiiorts have been made to produce the desired uniform wax crystals. However, so far as we are aware, the prior efforts have failed to solve this oil problem. The conventional dewaxing processes now in general commercial use produce a rather haphazard mixture of large and small wax crystals which reduce the rate of lltratlon, while trapping excessive quantities of oil solution in the mass of non uniform crystals on the filter.

The system herein disclosed involves special cooperative conditions which begin by deliberately forming a multiplicity of extremely minute wax nuclei crystals, and continue at successive stages where we have created conditions which progressively increase the growth of the selected minute nuclei crystals. Actual tests have clearly shown that these new conditions produce relatively large and approximately uniform wax crystals. The rate of filtration has been very profitably increased, and the yield of dewaxed oil was likewise increased. Furthermore, the wax product containing a relatively small percentage of oil solution, can be purified at a relatively low cost.

With the foregoing and other objects in view, the invention comprises all of the novel cooperative details herein shown and described, but it is to be understood that the scope of this patent extends to modifications and variations described by terms of the claims hereunto appended.

The drawing is a diagrammatical view of a dewaxing system embodying features of this invention.

- be produced in any suitable manner.

To illustrate one form of the invention we will describe details of a blending chamber I for the incoming oil and solvent, and also refer to adrawing specifically sets forth volumes of cooled solvent to be added at successive stages, as well as specific temperatures at such stages. However, it-

is to be understood that these speclc details are merely for a general comprehension of an unexpected new subject, and that the invention is not limited to such details. We desire to begin by producing an oil solution at approximately the cloud point of the solution, orwithin about 10 F. of the cloud point, and this can be accomplished in any suitable manner.

The drawing shows that the blending chamber I forms a relatively large elongated passageway, and that a continuous stream of the incoming oil charge from pipe 3 is transmitted through a heater 4 and thence through pipe 5 to one end of said passageway. A continuous stream of dewaxing solvent is transmitted from a pipe 6 and forced through a cooler 1 to a pipe 8 having branches 9 leading to successive stages in the elongated blending chamber I. The branches 9 are provided with regulating valves I0 set for gradual decreases in the admission of cooled solvent, as suggested by specific conditions set forth in the drawing. Under these conditions the slowly advancing mixed stream in the chamber I will be gradually cooled as shown at temperature indicators II. At the beginning there is a very rapid decrease in temperature, but this is followed by a carefully regulated decreased cooling for the purpose of merely producing a cloud point, or within about ten degrees of the cloud point.

We desire to carefully produce the extremely tiny wax crystals at the cloud point and thereafter uniformly increase the growth of each of these nuclei wax crystals. This cloud point may However, the` idea of carefully producing and then Very gradually enlarging the minute wax crystals seems to be a novel subject, involving special cooperative conditions.

The blending chamber I may be provided with a rotating shaft l2 provided with agitators I3 'wax nuclei crystals are gradually enlarged for the purposes of the invention herein disclosed. However, for convenience in briefly describing the invention, we have shown a single coil having an outlet 20 at the bottom leading to a chiller 2| where the mixture is subjected to comparatively rapid chilling, and then discharged through a pipe 22 to a conventional ltering apparatus including a rotary filter 23. The, dewaxed solution passes through the filter and escapes through a discharge pipe 24, while the wax crystals are deposited on the periphery of said lter, so as to form a. relatively thick wax cake which is removed at 25 and discharged through a conductor 26.

The coil 2 herein shown is associated with a source of dewaxing solvent which flows in a continuous stream under pressure from a pipe 21, and through a chiller 28 to a pipe 29 having numerous branches 30 leading to successive inlets of the cooling coil 2. Each branch 30 is provided with suitable regulating means diagrammatically indicated by valves 3|. The regulating devices are carefully adjusted to progressively increase the admission of chilled dewaxing solvent to the mixture advancing through the coil 2. A specic example of increases in the admission of chilled solvent appears at the left side of the coil 2. Study of this specific example will show that relatively small but progressively increasing quantities of the chilled solvent are injected during initial stages of the growth of the tiny nuclei crystals, so as to positively provide for most gradual and uniform preliminary growth during said initial stages.

'I'his involves one of the critical conditions in our plan for approximately uniform growth of the extremely minute nuclei crystals formed at the cloud point. However, as suggested in the specific example at the left side of coil 2, we can progressively increase the admission of chilled dewaxing solvent at subsequent stages to more rapidly increase the rate of growth of the wax crystals.

The linear velocity of the mixed stream in the coil 2 is preferably between one-fourth of a foot and three feet per second, and the pipe coil 2 is composed of pipes having progressively increasing diameters to avoid excessive increases in velocity in response to the admission of the successive solvent streams.

The temperature of the mixed stream in said coil 2 is preferably reduced at a rate between two and six seconds per degree of Fahrenheit temperature. A suitable decrease in temperature is shown in a specific example at the right hand side of the coil 2, where indicators 32 are connected to successive stages in the pipe coil.

The specic illustration of temperatures, relative volumes, etc., are merely an example of one of our testing operations wherein we employed a solvent blend of 95% isopropyl acetate and 5% amyl acetate to dewax a petroleum lubricating oil stock having a pour point of 100 F., and containing about 9% Wax. However, the invention is not limited to any specific solvent, nor to the specific example employed in describing the invention. Numerous other dewaxing solvents include methyl ethyl ketone which may be improved by adding toluol; acetone and benzol, isopropyl ether and butyl alcohol, methylene chloride and butyl alcohol, or any other suitable de'- waxing solvent.

The drawing refers to incoming oil at a temperature of 180 F., but this merely refers toour specific example. Lower or higher temperatures may be employed. The same is true of other conditions in the illustrative example. More specifically stated, the incoming oil from pipe 5 is preferably at a temperature between 125 F. and 180 F., while the cooled solvent from pipe il may be at a temperature between 35 F. and 65 F. The temperaturen! within about 10 of `the cloud point in pipes l5 and l1 may be between '75 F. and 95 F., the temperature of the solvent from pipe 29 may be 20 above or below zero; the mixture discharged at the bottom of coil 2 may be at a temperature between 30 F. and 50 F.,

and the resultant mixture may be quickly chilled in the chiller 2l and transmitted to the lter at any desired temperature. However, these specic temperatures are merely illustrative of desirable conditions, intended to more clearly set forth a specic arrangement of cooperative details, without limiting the scope of the patent to said temperature conditions.

In the second injection unit 2, we preferably adhere to a continuous stream line iiow, at relatively low velocities, as distinguished from a turbulent flow, so as to positively provide for free selective growth of the numerous individual crystals, which could not occur under highly disturbed fluid conditions. The gradual ejection of the wax out of its normal liquid state in the solution is progressively accomplished not only by very gradual decreases in temperature, but also by the progressive anti-.solvent properties of the solvent on the wax. We provide cooperative 40 conditions in this step by step procedure which produce a natural growth of a nearly perfect wax crystal from its minimum unit size to approximately uniform enlarged dimensions, thereby forming approximately uniform wax crystals for economical separation of the wax from the oil.

We claim: 1. In the art of dewaxing oils the process of forming approximately uniform wax crystals which comprises introducing a heated stream of wax bearing oil into an elongated blending passageway, injecting streams of relatively cool dewaxing solvent into the stream of wax bearing oil at successive stages 'in saidpassageway to gradually form a cooled solution containing minute Wax nuclei crystals at approximately the cloud point of the solution, thereafter injecting streams of colder dewaxing solvent into the stream of waxy solution at successive additional @0 stages to progressively deposit additional wax around said minute wax nuclei crystals, thereby gradually increasing the dimensions of the individual crystals, progressively increasing the volumes of said streams of colder dewaxing solvent at said additional stages to more rapidly increase the growth of the wax crystals, causing the'mixed stream in said additional stages to move at linear velocities between one-fourth of a foot and three feet per second, cooling the solution to the desired dewaxing temperature, and ltering the liquid solution from the resultant approximately uniform wax crystals.

2. In the art of dewaxing oils the process of forming approximately uniform wax crystals which comprises introducing a heated stream of wax bearing oil into an elongated blending passageway, forcibly mixing streams of relatively cool dewaxing solvent with the stream of wax bearing oil at successive stages in said blending passageway to gradually form a cooled solution containing minute wax nuclei crystals at approximately the cloud point of the solution, thereafter injecting streams of colder dewaxing solvent into the stream of waxy solution at successive additional stages to progressively deposit additional wax around said minute Wax nuclei crystals, thereby gradually increasing the dimensions of the individual crystals, separately regulating the flow of said streams of colder dewaxing solvent to provide for admission of relatively small but progressively increasing quantities of said colder solvent during initial stages of the -seconds per degree of Fahrenheit temperature,

separately cooling the resultant mixture to the desired dewaxlng temperature, and then ltering the liquid solution from the wax crystals.

EDDIE M. DONS. OSWALD G. MAURO. 

